This invention relates to liquid ring pumps for pumping gases or vapors (hereinafter generically "gas") to compress the gas or to produce a reduced gas pressure region ("vacuum"). More particularly, the invention relates to liquid ring pumps having a liner inside the stationary pump housing, said liner being free to rotate with the liquid ring to thereby reduce fluid friction between the liquid ring and the housing.
Liquid ring pumps with rotating liners are known as shown, for example, by Haavik U.S. Pat. No. 5,100,300 and Russian patent 939,826. In Haavik U.S. Pat. No. 5,100,300 the liner is supported for rotation by a pressurized bearing liquid in the clearance between the liner and the stationary housing. In Russian patent 939,826 gas is mixed with the liquid which supports the liner for rotation to reduce frictional resistance to rotation of the liner.
In liquid ring pumps the pressure of the gas being pumped increases as it progresses around the pump. As a result, there is a substantial net force acting in one radial direction on any rotating liner provided in the pump. This net force tends to push the liner toward undesirable contact with the housing at a location along the above-mentioned radial direction. The system for supplying the pressurized bearing fluid for supporting the liner must be effective to substantially prevent such contact without requiring wastefully large bearing fluid flow rates and/or pressures.
It is therefore an object of this invention to improve the supply of bearing fluid to liquid ring pumps having rotating liners supported by such bearing fluid.
As has been mentioned, Russian patent 939,826 shows that rotating liner bearing liquid friction can be reduced by mixing gas with the bearing liquid. The fluid frictional drag on the rotating liner can be reduced even more by completely or substantially completely substituting compressed gas for liquid as the rotating liner bearing fluid. However, there are several concerns associated with using compressed gas instead of liquid as the bearing fluid. One such concern is that if gas is to be used, the clearance between the liner and the stationary housing should generally be smaller than if liquid is used. A smaller clearance exacerbates the above-mentioned problem of possible contact between the liner and the housing in the radial direction of net gas pressure force. Another concern associated with using gas as the liner bearing fluid is that if the clearance between the liner and the housing is sized for gas, then liquid should be kept out of that clearance to the greatest extent possible to avoid the high drag that liquid in such a small clearance would produce. It may also be important to prevent or substantially prevent the liner bearing gas from escaping into the working space of the pump, particularly into the intake region of a pump operating as a vacuum pump. Such escaping liner bearing gas wastes energy and reduces the volumetric efficiency of the pump. It is also generally desirable to operate the pump with the smallest amount and pressure of liner bearing fluid (whether liquid or gas) that can be made to give satisfactory results so that energy is not wasted pumping excessive amounts of bearing fluid or pumping the bearing fluid to unnecessarily high pressure.
In view of the foregoing, it is another object of this invention to improve liquid ring pumps with fluid-supported rotating liners.
It is still another object of this invention to provide liquid ring pumps in which compressed gas can be more readily used as a bearing fluid for the liner.